The present invention relates to a composite sheet comprising two plies one of which has a large number of projections, and a process and an apparatus for producing the composite sheet. The composite sheet of the present invention is suited for use as an element, especially a topsheet, of absorbent articles such as sanitary napkins and disposable diapers.
JP-A-5-59655 discloses a bulky composite nonwoven fabric which is produced by adhering a spun-bond nonwoven fabric to at least one side of an elastic sheet material by point bonding to prepare a composite nonwoven fabric, stretching the composite nonwoven fabric in a prescribed direction, and releasing the stretching load to make the spun-bond nonwoven fabric wavy. This composite nonwoven fabric is used as a side belt of a pull-on diaper. Other known methods for obtaining composite sheets with a large number of projections include those disclosed in JP-A-10-245757 and JP-A-2-18036.
According to JP-A-5-59655, plastic deformation of the spun-bond nonwoven fabric is taken advantage of to make itself wavy, so that the wavy part of the composite sheet is fuzzy. When such a fuzzy sheet is used as a topsheet of an absorbent article, the fuzz would irritate the wearer's skin to reduce wearing comfort. Seeing that the composite nonwoven fabric is not contemplated for use as a topsheet of an absorbent article, its application as a topsheet of an absorbent article is not expected to prevent leakage of urine, still less a highly viscous liquid such as soft stool or menstrual blood.
Moreover, since the waviness results from plastic deformation of the spun-bond nonwoven fabric, it is difficult to always make protrusions of a given size with good reproducibility.